This invention relates to a power wrench and wrench assembly for making and breaking threads in sections of pipe and pipe couplings.
In oil and gas well drilling operations, the drill pipe is assembled in lengths joined with threaded joints. As the pipe is fed into a well, the sections of pipe are threaded together through couplings. When removing pipe, the threaded sections must be disconnected and the sections of pipe stored. Inserting and removing the sections of drill pipe is called "tripping." It will be appreciated that threading and unthreading sections of pipe on tripping in and out of the well hole can be a difficult and cumbersome job. To make up the threads (or unscrew or break the threads) requires relatively high torque (rotational force). "Spinning" the pipe section after breaking (or before making up) the joints requires much less torque and is accomplished at much higher speed. Tightening and breaking joints requires the wrench to be tightly clamped on the pipe. In the early days, tightening and breaking was done manually with hand wrenches (more recently with power assisted wrenches). Spinning is a separate operation, done by wrapping a chain around the pipe and pulling the chain with a winch. Today power tong wrenches are used. These ("roughnecks") have an open slot for pipe insertion and hydraulically powered clamps to grip the pipe. The wrench is rotated by a motor mechanically attached to the wrench. Mechanical attachment of the turning mechanism limits the turn of such wrenches to about 45.degree.. Such wrenches can develop high torque and work very well for making and breaking thread joints. It will be appreciated that these wrenches work in combination with a backup wrench that holds fast the other section of threaded joint. The wrench must be removed after making or breaking the threads, and a spinner (or top drive unit) attached to spin out the threaded joint. Such wrenches are exemplified by the description in U.S. Pat. No. 4,348,920. Some types of these wrenches lack the capacity of handling different diameter pipe without changing pipe clamps. Since drill pipe, couplings, tapered pipe and joints are of different diameters, a successful wrench must handle widely varying diameters--from about 3.5 to about 9.5 inches in diameter. It is a great advantage for a wrench to be able to accommodate a range of diameters without having to change the clamps. U.S. Pat. No. 4,979,356 is an example. of a solution to this problem. It describes a power tong wrench which can not only accommodate the desired range of pipe diameters but is also capable of making and breaking pipe sections and spinning the pipe. The ability to do both with the same wrench is highly desirable since it accomplishes with one connection step what previously required two or more connections with a wrench and spinner. The U.S. Pat. No. 4,979,356 wrench comprises an inner immediate and outer annuli which consists of halves that can be split to mount around the pipe. Gripping is accomplished by clamps; hydraulically driven by an actuator which has a reach sufficient to accommodate various pipe diameters. The difficulty with this wrench is that it must be manually clamped around the pipe and manually disconnected. It lacks the open slot pipe entrance of the "roughneck."
It would be very desirable to have a power tong unit that can accommodate various pipe diameters and that has the making, breaking and spinning capability of the U.S. Pat. No. 4,979,356 power tong and the ease of assembly of the slotted roughneck wrench. This is difficult to accomplish because of the mechanical connection of the clamp actuators and rotating assemblies.